This invention relates to a multiple-band mixer circuit for use in an LNB (Low Noise Blockdown Converter) in the outdoor unit of a satellite broadcast receiving station, which circuit is capable of receiving multiple bands of broadcast wave.
The conventional two-band mixer circuit contains two independent mixer circuit blocks to receive two bands, that is, the first and the second bands. To select either of the two bands, a selection circuit is connected to the two mixer circuit blocks, thereby allowing either of the mixer circuit blocks to operate. Two monitor circuits are connected separately to the two mixer circuit blocks, respectively, to check for the operation of the mixer circuit blocks. As a result, the two-band mixer circuit becomes large in size, thereby does not meeting the increasing demand in smaller components for a two-band mixer circuit-containing satellite broadcast receiving system.